At the center of Anuradhapura, behind a golden railing, grows the Sri Maha Bodhi -- a sacred fig tree believed to have been propagated from a cutting of the original Bodhi tree in Bodh Gaya, India, under which the Buddha attained enlightenment. The cutting was brought to Sri Lanka in the 3rd century BC by Sanghamitta, daughter of the Indian emperor Ashoka and a Buddhist nun. The tree has been continuously tended and documented ever since, making it the oldest historically authenticated tree in the world. It does not look ancient in the way you might expect -- the Bo tree regenerates, sending down aerial roots that become new trunks. But the site is ancient, and the veneration is continuous and deep. Pilgrims leave offerings of flowers and oil lamps around its base. Prayer flags flicker in the wind. You walk here barefoot on warm stone, and the air smells of incense and frangipani.

Three great stupas dominate the Anuradhapura landscape, their whitewashed domes rising above the forest canopy like artificial mountains. The Ruwanwelisaya, built by King Dutthagamani in the 2nd century BC, stands 338 feet high. The Jetavanaramaya, constructed by King Mahasena in the 3rd century AD, was one of the tallest structures in the ancient world. The Abhayagiri Dagaba anchors the northern monastery complex. Each stupa is circumambulated by pilgrims walking clockwise, right hand toward the monument -- the proper direction of devotion. The scale is difficult to convey until you stand at the base and look up. These are not temples you enter. They are solid structures, sealed reliquaries, their meaning expressed entirely through mass and height and the slow procession of people around their base. From the top of Mihintale, ten kilometers to the east, all three dagobas are visible, emerging from the tree cover like white islands in a green sea.

The details at Anuradhapura reward close attention. At the threshold of nearly every monastery lies a moonstone -- a semicircular carved stone representing the journey from the secular world to the sacred. The finest moonstone in Anuradhapura is exceptional for its size and the intricacy of its concentric bands of animals and lotus petals. At the Abhayagiri complex in the north, the Kuttam Pokuna -- twin bathing ponds -- demonstrate engineering as art. The Western Monasteries offer a different mood entirely: austere communities that rejected the opulence of the main monasteries and practiced a stripped-down orthodoxy. And at Isurumuniya, a rock temple near the Tissa Wewa reservoir, four famous carvings draw visitors -- including the Isurumuniya Lovers, a relief whose identity has been debated for centuries but whose tenderness is immediate.

Anuradhapura is not Pompeii. The ancient zone is vast -- comparisons to Siem Reap's Angkor are not unreasonable -- and you will need a bicycle, a tuk-tuk, or a full day on foot to cover it. But what makes Anuradhapura different from most archaeological sites is the weight of ongoing devotion. The stupas are not preserved ruins; they are repainted, repaired, and actively worshipped. Full-moon nights -- Poya days -- bring crowds to temples that stay open past 9 PM. Remove your shoes and hats at every Buddhist site, cover your shoulders, and walk clockwise around monuments with your right hand facing them. Do not turn your back to a representation of the Buddha for photographs. The monkeys -- particularly the macaques -- are aggressive and will steal anything left unattended. But these are minor logistics in a place that offers something rare: the chance to walk through a city that has been sacred for twenty-three centuries and has never stopped being sacred.